A digital copying machine, for example, has been commercialized as an image forming apparatus. According to the digital copying machine, when copying a document image, the document image is read by an image reading section. With respect to thus read document image, a specified image process is carried out by an image processing section. Then, image information in accordance with the specified image process is printed out by a recording section. Thus, according to such a digital copying machine, an image is copied onto a sheet of paper by using only the image processing functions that are provided in the digital copying machine.
In recent years, it has been proposed that a plurality of image recording apparatuses or other apparatuses be organized into a network. For example, unexamined Japanese Patent Publication No. 116834/1978 (Tokukaishou 53-116834) discloses an arrangement wherein a plurality of image reading apparatuses and a plurality of image recording apparatuses are connected through a control section. In such an arrangement, a document image that has been read by any of the image reading apparatuses is recorded, i.e., is printed by any of the image recording apparatuses.
Examined Japanese Patent Publication No. 36592/1995 (Tokukouhei 7-36592) discloses an image forming system wherein a plurality of copying machines, each having an image reading section and an image recording section, are connected to a control device. In such an image forming system, an image signal that is to be recorded is supplied to the copying machines in a distributed manner in accordance with a document copying mode that has been set, and copying operations are carried out by the copying machines in parallel with one another.
However, the conventional image forming systems have the following problems.
It is assumed that an image forming system has a plurality of digital copying machines. When carrying out the image process by use of a specified digital copying machine among the digital copying machines, the time required for the image process changes depending on the types of the image process or on the amount of image information to be image-processed.
Further, various image processing functions in the digital copying machine are dependent upon software. Here, with the recent remarkable developments of the software, the image processing functions have been highly improved in a very short period, and new copying machines having additional unprecedented functions have been newly introduced into the market. Consequently, for example, even when a digital copying machine having desired image processing functions is purchased, the digital copying machine, which has the highest image processing functions at the time of the purchase, will soon become outdated with relatively low functions in a short period.
In this case, it is impossible for the purchased digital copying machine to obtain functions higher than those originally provided in the digital copying machine. In the case where higher functions or newer functions are required, it is inevitable that a new copying machine has to be purchased to replace the older one. This tends to impose a big burden on users on an economic basis, and also to present an inherent problem for makers that try to provide consumers with new merchandise.